1. Field of the Invention
This invention generally relates to fluid flow measurement, and it particularly relates to a flow measurement apparatus that utilizes micro-electro mechanical system (MEMS) mass flow sensing technology to meter the gas dispensing and consumption in medical, consumer and general purpose industrial applications. This invention is further related to internet of things (IOT) that connect multiple devices and relay such information to the cloud computing in the ease of management and cost reduction.
2. Description of the Related Art
Gas dispensing and consumption are among the most common applications in gas metering. For example, oxygen dispensing to patients at hospital or to consumers in the form of home care; gas dispensing for instrumentation in laboratory and bottled special as, dispensing at industrial process lines. For industrial applications, there are millions of gas bottles or cylinder delivered daily worldwide. Up to date, each of those gas bottles or cylinders has a pressure sensor to monitor the gas consumption via the pressure rate inside the bottle and a gas flow meter made by variable area technology (floater or rotameter) to control the gas dispensing. While these kinds of devices are cost effective, they are far inaccurate for the metering of the accurate gas consumption or remaining volume of the gas inside the gas bottle. The pressure sensor is a mechanical one having a short dynamic range and full scale accuracy while the rotameter is also made by a mechanical approach with a fall scale pure volume output that is often affected by the variation of the environmental temperature and gas pressure. The inaccuracy would lead to difficulties in gas management and in most cases to huge waste of the gas in particular for the special gases used in industrial process. Further, it would also lead to loss of efficiency in work process if the gas consumption is under estimated. On the other hand, over estimation shall add unspecified cost to the gas consuming party. In some specific cases for the medical oxygen gas home care applications, the manufacture is often unprepared for the timely delivery of the gas bottle as no knowledge of the consumption of the oxygen can be registered in the controllable approach, and the manufacturers have to keep a huge inventory as for the varieties of the bottle capacities and consumption pattern, leading to the high cost of the manufacture and inventory management which is finally born to the users.
A typical as dispensing system has a gas container or a gas bottle in which the gas is highly pressurized. A gas dispense apparatus usually is installed on the gas container or gas bottle before the as dispense or delivery can be executed. The apparatus for the gas dispenser or container normally has a high pressure gauge that measures the pressure inside the gas container and another low pressure gauge that measures the pressure data in the dispensing or delivery line while a pressure regulating valve is placed at the middle of the two pressure gauges. These two pressure gauges are normally of pure mechanical type and insensitive to the full dynamic range of the gas to be dispensed. An example taught in the prior art in attempt for an improvement of the gas dispense for human oxygen dispensing (Steen, S. K., Oximetry device, open oxygen delivery system oximetry device and method of controlling oxygen system, U.S. Pat. No. 6,142,149, Nov. 7, 2000) shown a system that coupled with an oxygen saturation sensor and a flow sensor with a manual valve such that the oxygen information can be relayed for future reference. Such device still does not have the capability to alter the user in case the oxygen is completely consumed with risks at sudden cut-off of the gas supply from the gas bottle. A similar system disclosed by Frye, M. R. et al. (Frys, M. R., Brown, J. F. and Leithauser, D. R., Oxygen-delivery system with portable oxygen meter, U.S. Pat. No. 6,394,088, May 28, 2002) also does not have the capability to metering the oxygen consumption but a control function by the metering system.
Metering a gas container such as a tank or bottle is traditionally achieved via a weight station or similar weight devices or, in case of the form of a liquid under high pressure, a level sensor device that can be used to monitoring the remaining of the gas in the container (Northrop, C. L., Tank mass measurement assembly, U.S. Patent Application 2006/0130572, Jun. 22, 2006). Cohen, J. P. et al., (Cohen, Mattiola P. A. and Farese, D. J., Process for filling compressed gas fuel dispensers which utilizes volume and density calculation, U.S. Pat. No. 6,708,573, Mar. 23, 2004) taught a device that involved a complicated process to measure the volume, pressure and temperature of a pressurized fluid followed by consequently calculation that shall finally determine the mass values of the gas container. In a most recent disclosure (Wise, E. C., Method and apparatus for monitoring, communicating and analyzing the amount of fluid in a tank, U.S. Pat. No. 9,435,675, Sep. 6, 2016), a special device is proposed to monitor the remaining mass contain of a gas container. Inside the special device a flow meter is used to measure a plurality of flowrates that vary when being dispensed, and the embedded processor shall be used to determine the remaining mass and an indication shall then be generated by the device. However, the disclosed device for the gas consumption is based on the a rolling mean or average of a plurality of non-continuous measured flow rate that may be quite deviated from the actual mass as it also requires the knowledge of the gas density, pressure and temperature. The disclosed device has a capability to be remotely connected to a system comprised of a robot and a software application for the remote gas data management. While this does provide values to the management of the logistics of the gas bottles or cylinders, the actual user(s) of the gas containers are left out of the cycle as the user(s) must only be at the promise close to the gas containers in order to have the knowledge of the status of the gas bottles or cylinders which does not provide sufficient benefits for the actual user(s). In addition, this device is an additional unit, if direct attached to the high pressurized gas container, may have some safety risks and each pressurized gas container shall equipped with dual durable mechanical pressure gauge together with a pressure regulation mechanical valve that ensures the gas released from the pressurized container would not risk the applications. Attachment of the gas regulation valve before or after the disclosed device shall add excessive part which makes the operational inconvenient while the disclosed device shall also require external power source which adds other operational difficulties.